At the present time more and more axial-flow combines are used which radically differ from grain combines having a tangential threshing mechanism. In the axial-flow combines the processes of threshing and separating are integrated and intensified so that it is not necessary to install special devices such as straw shakers and agitators to separate residual grain.
The process of threshing and separating crop material in the axial-flow combines is quite different from that in the combines of conventional type. The crop material to be threshed in the axial-flow combine threshing mechanism moves along a helical line parallel to the rotor axis as distinct from the conventional threshing mechanism wherein the crop material moves at right angles to the drum axis.
A longitudinally arranged rotor threshes the oncoming crop material and at the same time causes it to move along a spiral path over a concave surface. The crop material is threshed due to combined beating and rubbing action exerted by working elements of the rotor and bars of the concave upon the processed material.
Tests of the axial flow combine with longitudinally arranged rotor showed its better performance as compared with the conventional combine. Due to its structural features the rate of threshing of the crop material and separation of grain from straw substantially increases; milder operation of the threshing and separating mechanism and use of rubbing action instead of beating action allow the extent of damage to the grain to be considerably reduced, which is especially important for enhancing the sowing quality of grain and for prolonging the storage life of food grain; the number of working elements of the threshing and separating mechanism is substantially reduced as one working element (axial rotor) fulfils functions of receiving and separating beaters, a threshing apparatus and a straw-walker.
Both in harvesting spiked grains and corn the axial-flow combine with the feed of crop material to the threshing and separating mechanism increasingly shows an approximately uniform and linear increase in grain losses behind the thresher, whereas the grain losses in the combine having a straw-walker increase progressively.
While featuring the above advantages, the axial-flow combine with the longitudinally arranged rotor has, however, a characteristic disadvantage residing in an offset of the grain threshed and passed through the concave to one side from the longitudinal axis thereof, and as a result a cleaning mechanism is unevenly loaded over its width which brings about grain losses behind said mechanism and a decrease in total grain output of the combine. This disadvantage is caused by that the crop material being threshed, when moving along a helical path in the threshing zone, is subjected to repeated actions of the rotor working elements and concave bars, which are not equal, and depend on the size of threshing clearance. The rate of sifting the threshed material through an open area of the concave is different. Besides, the grain passing through the concave under the action of centrifugal force is acted upon by two forces in different directions, namely by gravity and a force directed tangentially to the path of threshed material moving along an arc of a circle. Uneven distribution of the threshed grain passing through the concave results in uneven loading of sieves of the cleaning mechanism, which impairs the quality of its operation and decreases the total grain output of the combine.
Known in the art is an axial-flow combine (cf. U.S. Pat. No. 3,982,549, cl. A01 F 12/20) comprising a rotating rotor arranged along the direction of combine movement in a stationary cylindrical casing, an upper part of which mounts spiral guide fins on its internal surface, and its lower part in a threshing zone is provided with a grate-type concave under which is mounted a conveyor to transport threshed product separated through the concave to a cleaning mechanism.
A disadvantage of this prior art axial-flow combine resides in a one-sided offset with respect to its longitudinal axis of the material threshed and separated through the concave, its distribution across the conveyor in a layer of uneven depth and a further transfer of such a layer to a sieve of the cleaning mechanism, as a result of which the sieve is unevenly loaded over its width, the quality of operation of the cleaning mechanism is impaired and the total grain output of the combine is reduced.
One of the conditions for proper operation of the cleaning mechanism both in combines of conventional and axial-flow types is a supply of material in a layer of even depth onto the cleaning mechanism sieve over its width.
An uneven layer of the material moving over the sieve working surface cannot be fully blown through with an air current produced by a blower of the cleaning mechanism, and as a result unseparated grain together with chaffer is discharged from the combine, thereby decreasing the total grain output thereof.
Also known in the art is an axial-flow combine (cf. U.S. Pat. No. 3,556,108, cl. A01 F 12/32) having a transverse distributing means to evenly distribute material carried by a conveyor over a width of a cleaning mechanism sieve. A disadvantage of this axial-flow combine, which is characteristic of all axial flow combines, is a one-sided offset with respect to its longitudinal axis of the material threshed and passed through a concave to the conveyor and its further transfer to the cleaning mechanism, which impairs its operation. The transverse distributing means fails to perform effectively an even distribution of the material over a width of the sieve of the cleaning mechanism, as the material threshed and separated through the concave is distributed unilaterally across the conveyor and supplied in an uneven layer to the transverse distributing means, whose cross auger flightings have a different direction of helix and cannot evenly redistribute the material layer over the cleaning mechanism sieve.
Known in the art is one more axial-flow combine (cf. U.S. Pat. No. 4,177,820, cl. A01 F 12/20) wherein a rotor together with a stationary cylindrical casing and a concave embracing it from above and below, respectively, is offset towards one of the vertical walls of the combine body on the side opposite to the direction of rotor rotation. The opposite vertical wall mounts an angularly adjustable deflector. Although installation of one or even two deflectors (on both vertical walls) facilitates passage and concentration of threshed product separated through the concave near to the conveyor axis of symmetry, it does not provide for its even distribution over a width of the cleaning mechanism sieve.
Thus, the prior art axial-flow combines distribute the threshed product in a layer of uneven depth over a width of the cleaning mechanism sieve, which impairs the proper operation of the cleaning mechanism, brings about unjustified grain losses behind the combine and decreases the total grain output thereof.